The flag is white with a red saltire. Above this saltire appear the arms of Jersey.
Pascal Vagnat, 14 March 1996

The current flag was officially hoisted for the first time in 1981 (bicentenary of the battle of Jersey) although the proposal for the adoption of a new flag dated back to the Queen's Silver Jubilee year of 1977. The States of Jersey approved the new design on 12 June 1979, with only two votes against. The Queen officially issued the proclamation of the new flag on 10 December 1980.

Strictly speaking, the crown above the arms on the flag is not part of the arms of Jersey and was a new device introduced for some heraldic reason (potential confusion with use of the three leopards by England, I gather). The crown is described as being of 'ancient type' and is commonly called the Plantagenet crown.

Although St Patrick had nothing to do with Jersey, a red saltire on a white ground is commonly called St Patrick's cross. There may not be any sound evidence linking Saint Patrick, as a person, to a red saltire on white, but the connection, between St Patrick, as a name, and a red saltire on white, was made when the Order of Saint Patrick was established in 1783, and extended when the term "Crosses Saltire of St Andrew and St Patrick" was used in the blazon of the Union Jack in 1801.
David Prothero, 25 January 2001

According to "Portrait of the Channel Islands" by Raoul Lempričre, 1970 [i.e.,
before the advent of the current flag], p.155, in the middle of a discussion of
flag and arms in use on the Channel Islands, it is stated,

"In Jersey the
Union Jack is flown from the flagstaff on the western bastion of Fort Regent. By
tradition the flag is never half-masted except on the death of the Sovereign.
The lieutenant-governor of each bailiwick has his official flag, which is the
Union Jack with the arms of the Bailiwick at its centre. In Jersey it is flown
from the flagstaff in the grounds of Government House at all times when His
Excellency is in the island; it is never half-masted unless the
lieutenant-governor dies and is only hauled down when he leaves the island or
vacates his appointment. The flag is also flown on the bonnet of the l-g's motor
car when he is travelling about the island and from the masthead of any ship in
which he is embarked. Similar remarks apply to Guernsey.

The Jersey flag
is the cross of St. Patrick, which is described heraldically as a saltire gules
on a field argent. The insular colours of red and white are presumably derived
from those of the flag. It would appear that the cross of St. Patrick became the
Jersey flag as the result of a mis-reading of an entry in an 18th century book
of charts. It is not possible to prove the adoption of the flag before about
1841.Jarig Bakker, 27 October 2005

In what period has the St. Patrick's cross been used in Jersey?
Nozomi Kariyasu, 21 January 2001

Since about 1830 until the shield was added in 1981. Several lines of evidence exist for its use in this period:

Here is an extract from the translation of a letter written by the Bailiff of Jersey to the Lt-Governor in 1906: "As I have stated in previous correspondence the distinguishing flag formerly used by Jersey vessels - notably during the period (extending over several centuries) throughout which the Channel Islands enjoyed the privilege of neutrality in the wars between England and France (as to which consult Le Quesne's Constitutional History in Durell's edition p.p. 116-174 and Notes p.428-9) to ensure immunity, was the red St Andrew's cross on white ground, to this day called, and in local use as, the 'Jersey Flag'. Venables Vernon." Public Record Office, HO 45/10061/B2262.
David Prothero, 22 January 2001

The Bailiff of Jersey's reference to its earlier use is very vague. One might guess that he is perhaps referring to what is known as the Hundred Years War of the 14th and 15th centuries. A letter written by the Secretary to the Government of Jersey in 1938, quoted in Flag Bulletin Jan/Feb 1983, refers to a Papal Bull granted by Pope Sixtus IV (1471-1484) confirming the privilege of neutrality, but its significance in relation to the flag is disputed. I shall see if I can borrow a copy of the book that is mentioned by the Bailiff.
David Prothero, 25 January 2001

A flag book called Neptune François published at Amsterdam in 1693 showed a red saltire on white as the Irish flag. This was copied by several later publications. A Dutch book of 1700 (De
Doorlughtige Weereld) says the following: 'Yrland heeft een witte Vlag, met een rood Andries Kruys' ('Ireland has a white flag, with a red Andrew's cross'). This publication seems to have had one interesting effect: the illustration of the red saltire was captioned 'Ierse' ('Irish') in this and in later Dutch publications. An English author, Carington Bowles, misunderstood the Dutch caption and showed the red saltire as the flag of Jersey in his Universal Display of the Naval Flags of all Nations (1783), thereby giving the island the flag which, slightly modified, it still uses.
Vincent Morley, 20 January 1997

The theory about the origin of the flag quoted above is, I submit, of dubious value. This is NVL Rybot's theory which is hotly disputed. No evidence has ever been presented to show that the flag was adopted by Jersey after the Dutch mix-up, or any reason why a flag with no administrative status should be whole-heartedly adopted by a French-speaking population on the basis of a Dutch/English linguistic confusion. The case that the Dutch were confused simply because Jersey and the Irish were indeed using the same simple device has never been refuted. There is a theory that the red saltire was adopted by Jersey ships at an earlier period as a variation of the cross of St. George in order to distinguish themselves from English ships and thus demonstrate their neutrality.

The clinching argument for the adoption of a new flag was that the traditional red saltire had never been proclaimed officially and that its use was simply traditional custom. The traditional flag was supposedly not distinctive (or 'distinguished') enough to be adopted officially. The question of the new flag raised passions. Many saw no need for the flag to be changed at all. A strong body of opinion would have preferred les trois léopards (the Island's three leopards) simply shown on the flag - or possibly the two leopards of Normandy. The flag with the three leopards (gules three lions passant
guardant) is indeed the one that hangs over the Bailiff's chair in the States chamber. The current flag appears therefore to be a compromise between different opinions.
Geraint Jennings

This flag is in Norie/Hobbs (1848), on the flagchart of Laurie (1842) on p. 70 of Wilson's Flags at Sea (1986), and discussed extensively by Carr/Barraclough in "Flags of the World". In my opinion the reference in these books to the St. Patrick's cross looks spurious, based on references in Irish history books, and dubious images on Dutch flagcharts, where 'Ierse' might be read as 'Jersey'. However the images of Norie/Hobbs 1848 and Laurie (1842) seem to indicate that by that time the Jersey flag was used extensively - while it is not present on previous British flagcharts in Wilson's book.

Barraclough's "Flags of the World", 1971 has this to say: "Jersey uses a white flag charged with a red diagonal cross. Although this flag has yet to receive the formal recognition of H.M.Government it appears to have been established as the island's territorial flag for well over a century. (...) This flag is flown on all official occasions on public buildings, as well as on business establishments.
Jarig Bakker, 21 January 2001

The international flag book by Christian Pedersen (1971) mentions that Jersey state flag - the same as the St.Patrick's Cross-has been used as the territorial flag of the island for just over a century,without however being formally recognized by the British Government. He also mentions that Jersey Lieutenant Governor's flag is the Union Flag charged in the centre with the arms used by the States of Jersey,which are identical with the first and fourth quarters of Arms of England. These are placed on a white roundel within a green garland.
Nozomi Kariyasu, 26 January 2001

Flags & Coats of Arms by William Crampton (1985) mentions that the flag of Jersey has a white field charged with a red saltire of St.Patrick and in the top triangular field there is a red shield with three gold lions passant guardant (this was granted to the island as a seal by Edward I in 1279) ensigned with the crown of the Plantagenets and in this form the flag was approved on 7 April 1981 and without the arms it was used unofficailly for a hundred years.
So I assume that the flag without arms were used c.1870 until 1985.
Nozomi Kariyasu, 26 January 2001

It is interesting to recall that when the Channel Islands were occupied by Germany during World War II, this flag was worn as an ensign by ships carrying passengers and cargo between the islands - the use of the Red Ensign being, for obvious reasons, out of the question!"
Jarig Bakker, 21 January 2001

In 1905 the Home Office suggested that Jersey and Guernsey should apply for arms so that the badges used on the defaced Union Jacks of the Lt-Governors would be properly warranted. It was pointed out that the arms of Man were already on record and that the College of Arms, would extend to the Channel Islands, the special arrangement by which colonies were granted arms for a reduced fee. Jersey and Guernsey replied that they were granted arms by Edward I in 1277 and 1279 respectively, but perhaps the College of Arms was not aware of this, not having been incorporated until 1484. Garter King of Arms replied that a small differencing was advisable to distinguish the Arms of Jersey from the English Arms, "in order that the Arms of England might not be used pure by a dependent state of the realm." However continued use of Arms of Jersey, Guernsey and Alderney "as previously granted" was approved by the King.
David Prothero, 31 January 2001

The arms of Jersey are gules three lions passant guardant. The Lieutenant-Governor flies a Union Jack with the shield of arms on a white disc surrounded by a garland in the centre of the flag.
Roy Stilling, 14 March 1996

The Jersey Ships' Registry is pleased to announce that the States Assembly
has today [23 June 2010] unanimously approved the use of the Jersey Defaced Red
Ensign by all ships registered at the Port of Jersey. The design of the flag
(copy attached) has also received Her Majesty the Queen's approval.

The
flag may be flown from all Jersey registered vessels, registered as either
'full' (Part 1) or Small Ships Register (SSR), under the Shipping (Jersey) Law
2002, for vessels up to 400 tons. The use is entirely optional, with the plain
red ensign still applicable. Flags may be purchased from local chandlers.

Further details
on registration are available at:
www.gov.je/shipsregistryDebbie Podger to Piers Baker, forwarded by
Clay Moss, 24 June 2010

The Jersey Government ensign is worn by harbour and fishery protection vessels.
Jersey currently does not have a defaced red ensign for use by vessels on its
registry, apparently because the shipping register wishes to attract ship owners
who want a plain red ensign but don't want the bureaucracy of the MCA who
administer the British civil ensign. When I finally persuade them to add it as
an alternative ensign it should look just like the blue, but with a red field.
In the meantime I suspect that the blue ensign is used as a courtesy ensign by
some vessels.Graham Bartram, 28 May 2007

The Channel Island of Jersey is on its way to adopt its own version of a red
ensign. The boat owners who are going to fly it, are invited to give their
opinion about the design, prepared by the College of Arms in London. Posted
on:
http://www.gov.je/Travel/MaritimeAviation/BritishRegisterShips/Pages/ProposalJerseyRedEnsign.aspx
(no longer available). This site also provided an illustration of the proposed
red ensign.Jos Poels, 9 April 2010

Here is news from Jersey: "Jersey boats may fly own ensign"Jersey-registered
boats could fly their own version of the UK's Red Ensign after the Queen
approved a new design. The ensign is a red flag, with a union flag in one
corner, flown from British-registered ships to show their origin. Other crown
dependencies have a defaced version, carrying a badge or crest, and Jersey's
maritime authorities have sought one for the island. The ensign, with Jersey's
coat of arms and a crown, needs additional approval from the States before it
can be used. The States has opened the design up to public consultation and is
welcoming comments on the move until the end of the month. The government said
the crown used is the Plantagenet crown, dating back to King John, which
symbolises the link between Jersey and the British Crown.Source:
http://news.bbc.co.uk/2/hi/europe/jersey/8611235.stmJens Pattke,
10 April 2010

In 1905, the Harbour Master of St Helier applied to the Admiralty for a badge for a Blue Ensign that would be "plainly distinctive and easily distinguishable from the special Blue Ensign of the Royal Channel Islands Yacht Club, and from the ensign used by Guernsey authorities, a three leopard badge surmounted by a sprig of laurel." The ensign was needed to identify the steam-tug "Duke of Normandy" to the French who had granted it the privilege of official recognition and immunity as a vessel in public service. This placed the "Duke of Normandy" on the same footing as tenders of Trinity House who were not charged harbour dues. States of Jersey were the registered owners and the ship would fly the Blue Ensign only when on government service. The badge on the Blue Ensign of the R.C.I.Y.C. was three yellow lions on a red shield ensigned with a crown. The proposed badge was a red saltire on a white rectangle surmounted by a yellow bordered red shield charged with three yellow leopards ensigned with a crown.

The request was not well received. The Home Office were aggrieved because the application had been made direct to the Admiralty, and not through them, and the Admiralty considered that the application should be refused because Jersey was not a colony, the States were not a public office, and therefore the Order in Council authorising Blue Ensigns did not apply. It was finally decided that it could be granted as a special case under Sec.73(i) of the Merchant Shipping Act 1894; "any other ship or boat for the time being allowed to wear any other national colour (other than the Red Ensign) in pursuance of a warrant from His Majesty or from the Admiralty." Thus the warrant that was sent in March 1907 stating that the badge of Jersey in the fly should be the arms, was for one particular ship, and was not extended for general use by any vessel operated by the States of Jersey until 1997.
David Prothero, 31 January 2001

The States of Jersey boats were on display at the Harbour this weekend and I managed to get a decent shot of the ensign.

Here's an extract from the warrant dated 2/3/1907:

By the Commissioners for Executing the office of Lord High Admiral of the United Kingdom of Great Britain and Ireland, etc.
Whereas We deem it expedient that the steam-tug "Duke of Normandy," belonging to the States of Jersey, shall be permitted to wear the Blue Ensign of His Majesty's Fleet, with the Badge of Jersey in the fly thereof, namely, gules - three leopardised lions, passant guardant, or, in a shield.

By my calculations the shield as shown in BR20 (including fimbriation) has
proportions of 16:13, centred on the fly half and is 8/15 of flag width high,
whilst the fimbriation (to be taken off those sizes) is 1/120 of flag width
wide. Based upon a flag of 120 x 240 units these would give figures of 60-60
for the hoist, 120-34-52-34 for the top edge and 28-64-28 for the fly with
the fimbriation at 1 unit wide (thus a shield - excluding fimbriation - of 62
x 50 units).

Interestingly enough, all three Warrants (those of 1907,
1967 and 1997) I have in my collection allow Jersey to fly a defaced Blue
Jack to match the ensign, but I was assured by the harbour master that only
the Duke of Normandy has a jack staff from which to fly any such and that
they had no immediate plans for having one made.Christopher Southworth,
10 October 2008

The 1939 Flaggenbuch gives the size of the square jack's defacement as being
1/4 of flag width, however, BR20 shows the defacement on the jack of the Royal
Fleet Auxiliary as being 9/24 of flag width high, and this would be a reasonable
indication (or at least a starting point) for any illustration of a jack for
Jersey.Christopher Southworth, 10 October 2008

image by Clay Moss, 13 October 2008

In this version I compromised between Neubecker's suggestion of a badge being
1/4 the width of the jack, and the other standard that I am familiar with, 2/9.
I have made it 17/72.Clay Moss, 13 October 2008

2/9 makes sense in view of the of the fact that the fly half of a Square Blue
Jack is has exactly one-half the area of that on a Blue Ensign. Neubecker's 1/4
was, in any case, illustrated by a white disc, so again 2/9 for a shield without
a disc makes sense.Christopher Southworth, 13 October 2008

Based on a phone call to the harbour master in Jersey, the only vessel the
Jersey Authorities have which possesses a jack staff is their main tug the 'Duke
of Normandy', and that they had no plans (short of a state visit by Her Majesty)
to obtain a jack for same.

A defaced Blue Jack is authorized by the
Warrants that permitted a defaced Blue Ensign and accordingly it exists on
paper. It has not yet appeared in the cloth. The Admiralty Warrant of 1907 was
for a defaced Blue Ensign and matching Jack for the steam tug Duke of Normandy,
whilst that of 1967 was for a tug of the same name. My enquiries yielded the
fact that the original steam tug was replaced by a motor vessel in 1967, but
there is no reason to suppose that a Jack was not flown sometime during the
sixty years of the steam tug's service. The 1967 tug only lasted thirty years
and was replaced in 1997, but the MoD Warrant of that year covered the tugs Duke
of Normandy and Duchess of Normandy so it is these two vessels (but no others)
that are now entitled to wear both ensign and jack.Christopher
Southworth, 13 October 2008

Image based on a photograph by Crawford van Horne, 26 June 2015.
Also in the photograph was an equivalent flag with a red field.

The logo featuring the golden bird symbol represents Jersey’s sense of
independence, spirit and enterprise. This mark is intended to embrace and
promote all aspects of Jersey. It is optimistic and outward looking (and not
parochial or inward focussed). It represents Jersey as an attractive destination
in which to live, visit, work or do business. Its attitude is one of great
optimism and enthusiasm depicting the symbol literally taking-off and soaring.
It is warm in colour and energetic in spirit."Source:
http://www.jersey.com/business/Brand/Basic-Brand-Elements/Pages/default.aspxZoltan Horvath, 27 June 2015

Flag flown on island's bare poles
Jersey pennant
The new pennant flag will be flown on flag poles when the standard flag is not.
A new flag has been designed to be flown on flag poles in Jersey which would otherwise be bare.
The triangular pennant, or storm flag, has been designed to withstand strong winds so it can be flown all the time.
Chris Scholefield, of Jersey Heritage, said the flag would be used on days when the standard flag, saved for key dates, was not being flown.
Jersey Heritage plans to raise the new pennants on 12 poles at the Maritime Museum later.
They will be raised in a ceremony by 12 cadets from the Victoria College Combined Cadet Force.
The new 2m (6.5ft) flag carries the Jersey crest.

Mr Scholefield told BBC Jersey: "This is to avoid having a bare flagpole - it's not instead of the Jersey flag, it's as well as, it's an extra one.
"So much of the time you see bare flag poles, those are the ones that can start flying this new Jersey pennant, or storm flag.
"When red letter day comes along and you want to put up your normal Jersey flag, down goes the storm flag, up goes the standard flag and then the storm flag can replace it when the standard flag comes down."

Chrystian Kretowicz, 1 May 2010

The flag is a long triangular pennant, white edged red, with the minor arms
(as on the flag) on the center hoist area.António Martins-Tuválkin,
2 May 2010